Biodiversity, it's very definition, implies diversity, which arises from the existence of thousands, tens of thousands of species within any given ecosystem. This then results in the ecosystem being able to provide its services, known collectively as ecosystem services. The goal is to protect biodiversity by protecting ecosystems. A general technique for doing so is to declare a top level species within its respective ecosystem as endangered (because it is endangered or will become extinct if its ecosystem is destroyed) as an umbrella species, otherwise known as a keystone species. The ecosystem is then preserved under the umbrella of the umbrella species. This protects biodiversity. I gave a general summary of this process by drawing attention to the Spotted Owl controversy and what it was all about in this post: https://bitcointalk.org/index.php?topic=96217.msg1061023#msg1061023

We can get into all kinds of discussions as to what biodiversity is, what threatens it, where you'll find it, why it needs to be preserved, and how preservation is affected.

Your example of relocating the Scimitar Oryx is simply not a case of protecting biodiversity. What they did is not necessarily a bad thing, but your usage of it as an example to protect biodiversity simply shows that you have a lot to learn about the subject.